Siri may be your personal assistant. But your voice is not the only one she listens to. As a group of French researchers have discovered, Siri also helpfully obeys the orders of any hacker who talks to her—even, in some cases, one who’s silently transmitting those commands via radio from as far as 16 feet away.

A pair of researchers at ANSSI, a French government agency devoted to information security, have shown that they can use radio waves to silently trigger voice commands on any Android phone or iPhone that has Google Now or Siri enabled, if it also has a pair of headphones with a microphone plugged into its jack.